Cellulose is a major component of plant fiber, e.g. cotton fiber. Cellulose is composed of crystalline beta-1,4-glucan microfibrils (see World Patent Publication No. WO 98/00549). These microfibrils are strong and can resist enzymatic and mechanical degradation and are important in determining nutritional quality of animal and human foodstuffs. Hence, modification of the biosynthetic pathway responsible for cellulose synthesis through modification of cellulose synthase activity could potentially alter fiber quantity, either by producing more or less fiber in a particular plant species or in a specific organ or tissue of a particular plant. Modification of cellulose synthase activity could increase the value of the fiber to the end-user and may improve the structural integrity of the plant cell wall. Lastly, because cellulose is a major cell wall component, inhibition of cellulose synthesis would probably be lethal. Thus, cellulose synthase may serve as the target for a novel class of herbicides. Plant cellulose synthase genes, homologs of the bacterial celA genes encoding the catalytic subunit of cellulose synthase, have been reported from cotton, Arabidopsis, corn, rice and alfala (Arioli et al. (1998) Science 279:717-720; Holland et al. (2000) Plant Physiol 123:1313-1324; World Patent Publication Nos. WO 98/00549, WO 98/18949, and WO 00/09706).
There is a great deal of interest in identifying the genes that encode proteins involved in cellulose synthesis. These genes may be used in plant cells to control the synthesis of cellulose. Accordingly, the availability of nucleic acid sequences encoding all or a portion of a cellulose synthase would facilitate studies to better understand cellulose synthesis in plants and provide genetic tools to alter cellulose production.